The Rivals100 Five-Star Challenge presented by Under Armour featured the top prospects in the country on the field at Soldier Field in Chicago. Here is what we learned about Team Tumblr at the event.

Kirk has more to offer

Christian Kirk's skill level was never really in doubt. The underclassman would not have been invited to the event if it was.

The fact that he landed on the first day's list of top performers, however, was a bit of a surprise. No defensive back at the event could handle Kirk in one-on-one drills, as the junior-to-be used his speed and violent change of pace to beat elite defensive back prospects in the class above him. His smooth and sudden transitions out of cuts were truly something to behold.

Kirk has 17 scholarship offers, and that number will almost certainly double in his two final season of high school football. There's no doubt that he is the top underclassman in Arizona. The conversation now is about where he fits nationally. He's a little shorter than what is ideal for a wide receiver, but the weekend he had in Chicago tempered that concern.

Dupre belongs in the conversation

So much for Iowa State commit Allen Lazard being alone at the top of the list of 2014 wide receivers. It's clear that River Ridge (La) John Curtis standout Malachi Dupre has the ability to challenge him.

Dupree got everyone's attention on Saturday afternoon and captivated onlookers until the event's finish. Most times, he looked like the best route-runner in attendance and used his size-speed combination to frustrate every defensive back he matched up against. He was the most dynamic weapon on his 7-on-7 squad -- a team that also included Lazard. Dupre is ranked as the No. 5 wide receiver in the nation but was much better than that in Chicago.

Heard has room for growth

Jerrod Heard does a lot of things well. That was apparent on the first day of competition. Heard was the top quarterback performer on Saturday, a day that saw him throw hyper-accurate strikes to receivers during one-on-one reps. He showed he could make all of throws and rarely muscled a pass.

Then, 7-on-7 happened.

When forced to make multiple reads, Heard was often overwhelmed.

He locked in on receivers and routinely forced passes to blanketed targets despite having open options elsewhere. Rare was the occasion that the Texas commit surveyed both sides of the field before releasing the football.

The good news is that, aside from having the ability to make plays with his feet, Heard has a good arm and is mechanically sound. The bad news is that he needs serious work when it comes to surveying the field. The finished product will be determined by how he responds to coaching.

In the conversation

Fort Worth (Texas) All Saints offensive guard Demetrius Knox entered the Rivals100 Five-Star Challenge as the top offensive guard in the country and a Rivals100 prospect, but he also had a chip on his shoulder. He wanted to show he not only had the talent to be the top offensive lineman in the country but also had the nastiness and intelligence to dominate. He wasted no time by setting the tone on Saturday. His long arms, his muscled-up lower half and his feet made him stand out, but his intensity in one-on-ones really separated him. He made a statement that he was a force to be reckoned with and only lost one rep the entire weekend. It is safe to say he caught the attention of everyone.

Mama not far behind

Team Tumblr had a great weekend with guard play. Knox and Bellflower (Calif.) St. John Bosco offensive guard Damien Mama had the most dominating offensive line performances. In fact it was Mama who took home offensive line MVP honors after a hamstring injury kept Knox out of the last half of the Big Man Challenge on Sunday. Mama stepped up and set the tone for his team. He played with surprisingly quick feet and even more surprising endurance. He never seemed to tire and he was always there smiling, laughing and encouraging teammates. Mama's quick hands and strong punch were tough for even the top defenders to handle.